This could be the way to get Fractal Robots to work. Consider making a building where the walls are hexagonal columns of stacked drones. With enough of these (made for a dollar each perhaps) you could build a structure in a minute or so. Not sure how to seal the top though. Maybe drones could collect construction material to finish the structure off, like birds.

It would be cool if stable sections of drones could break away when in flight, say when their batteries are getting low, to be replaced by freshly charged units flown up, you could have a core structure remain aloft indefinitely.